The present invention relates to a lens unit for a projector and, more particularly, to a lens unit for a projector having two image lenses between a lamp and a liquid crystal display (LCD) panel.
FIG. 1 is a view schematically showing the optical arrangement of a conventional projector in which four image lenses are provided to represent a color image with one LCD panel. As shown in the drawing, while passing through an aperture member 12, the light emitted from a lamp 10 and reflected by a parabolic mirror 11 becomes a rectangular light having a ratio corresponding in length and width to a screen (not shown). The light becomes a uniform light as it passes through a scrambler 13, and then is inputted to an image generating means after passing an image lens 14, a hot mirror 15 for allowing infrared light to pass and a collimating lens 16 for converting the input light into a parallel beam. The image generating means includes polarizing plates 17 and an LCD panel 18 disposed between the polarizing plates 17 for generating an image as the input parallel beam passes through the rear side thereof. The image generated from the image generating means passes a condensing lens 19 and a projecting lens unit 20 comprising a mirror 21 and a plurality of lenses 22 for determining the degree of focus and magnification ratio of the image. Thereafter, the light is reflected off of a total reflection mirror 23 arranged at a predetermined angle behind the screen inside a cabinet (not shown), and thus magnified and projected to the screen.
The image lens 14 and the collimating lens 16 are optical members for uniformly distributing the uniform light passing through the scrambler 13 to the entire surface of the LCD panel 18. The image lens 14 magnifies the light passing through the scrambler 13 to a size of the LCD panel 18 and the collimating lens 16 converts the magnified light into a parallel beam. For such functions, the image lens employed in a conventional projector is comprised of four lenses. In such a case, however, the arrangement of optical elements is restricted and product costs becomes high due to the numerous number of parts.